gas vs electric boiler

Interesting discussion. I have installed the necessary pex tubing in my basement and garage for radiant heating. I was about to purchase a 155,000 BTU condensing high efficiency propane boiler (natural gas not available in my area), and my supplier recommended using a modulating electric boiler instead. He said operating cost, as well as initial cost would be cheaper. His claim was that the electric boiler would monitor the return and supply temperature of the water, and only use enough energy to re-heat the supply water to the required temperature. This would save money because, in the hydronic radiant system, the boiler does not operate all the time, and that the propane boiler would waste energy because it fires up "at full capacity" thus wasting energy. So, even though the conventional wisdom that gas is more efficent than electricity for heating water, the cost of using an electric boiler for this application will be lower.

Comments

Been thinking about gas vs electric boilers. Assuming that gas and electricity are the same price/unit. Which energy source is more efficient? Advantages of one vs the other? I have had customers ask me this question before... I have always answered with the fact that there is really no energy loss in heat transfer from element to water, whereas maximum efficiency of your mod con boiler (combustion) is 98%. I also know that it takes longer to heat up with electric elements vs gas.

My take is that while in theory electricity is 100% efficient at the house it takes three times the amount of fuel to make it and transport it to the home, due to transmission losses. In other words if you need 1 gallon of gas at the home to heat a cup of water it will take 3 gallons of gas at the plant to heat that same cup of water. By the time it gets transported to that home 2 of those gallons will be lost to heat and other losses along the way.

electric boilers to be along the lines of 99%. I'd call the mod con more mid 90%.

It's the electricity from a lump of coal to your door that looks bad, around a 30- 33% efficiency there.

Electric boilers are gaining more interest. Several electric suppliers are offering off peak rates now for residential customers. If you could get power for 3, 4, 0r 5 cents a KWH, that starts to look pretty good.

I just recievied a very nice electric boiler out of Minnesota. Electro-Boiler from www.electromn.com Very nicely crafted and a unique control board option to drive ZVs or pumps for zoning. Outdoor reset and common elements for replacement.

In my area the choic is LP or electric, and solar of course. LP phobia has more and more folks looking at electric.

As soon as Perry gets us that uber thermal storage product on the market

hot rod

Bob "hot rod" Rohrtrainer for Caleffi NAThe magic is in hydronics, and hydronics is in me

Although I am installing a condensing gas boiler in my house, I am providing power to the boiler room for a possible future electric boiler. I'll have a set up at the main electric panel for future photovoltaic, hoping that material costs will come down enough to make it cost effective. I haven't run the numbers yet. Anyone else considered this possibility?

in electric boilers. No expensive inducer fans, for sure. Issues with fuel leaks from seismic, tornados, etc is eliminates. No combustion air requirements. Very small packages, Check out the Laing combo heater and circ pump for small electric jobs. They work great and run forever.

Virtually any plumber or electrician with a meter could troubleshoot and repair an electric boiler. No combustion analyzer required?

Electric boilers can be mounted most anywhere, including bedroom closets, below floors in crawl spaces, etc.

Like any choice there are pros and cons.

hot rod

Bob "hot rod" Rohrtrainer for Caleffi NAThe magic is in hydronics, and hydronics is in me

in electric boilers. No expensive inducer fans, for sure. Issues with fuel leaks from seismic, tornados, etc is eliminates. No combustion air requirements. Very small packages, Check out the Laing combo heater and circ pump for small electric jobs. They work great and run forever.

Virtually any plumber or electrician with a meter could troubleshoot and repair an electric boiler. No combustion analyzer required?

Electric boilers can be mounted most anywhere, including bedroom closets, below floors in crawl spaces, etc.

Like any choice there are pros and cons.

hot rod

Bob "hot rod" Rohrtrainer for Caleffi NAThe magic is in hydronics, and hydronics is in me

"Assuming that gas and electricity are the same price/unit." Were you referring to the cost of the boiler? Maybe I missed something here?

I think you need to look at the cost of the fuel more than the cost of the boiler. Determine how many btu's you can buy for a dollar, then apply the expected system efficiency to see how much heat you get to delivery inside your home.

Simple example, if a gallon of oil costs $3 and has 140,000 btu's, that means you bought 46,666 btu's for a dollar (140,000/3). Now assume 82% efficiency, you get to keep 38,266 btu's in your house (46,666 *.82).

A kilowatt hour of electricity (kwh) has 3,412 btu's. If a kwh costs $.25 , that means you can by 4 of them for a dollar = 13,652 btu's ( 4 * 3,412). To make things simple, lets assume 100% efficiency for the electric boiler.

Based on this example, oil got us almost 3 times as much heat as electricity. You can go through a similar exercise for gas.

I expect you will find that electricity, despite its 99% efficiency, will cost substantially more than any other fuel when it comes to heating.

This is why you rarely see electricity as the principal mode of heating in a residential application (excluding heat pumps). Along the Saint Lawrence or the Colorado River - different story possibly - hydro electric no burning of secondary fuel.

I posted an article that should help you with what ever fuels you may want to compare.

An electric boiler is 100% efficient. They hang on a wall, require no chimney, last almost forever (except the elements), have great reliability, and are used in parts of the country with cheap electricity, Midwest, and West. An apartment owner can use one for each unit and have accurate readings as to heating usage. They are available in ratings from 10KW to 30KW, which will do a nice sized house. Available from efmheating.com

The problem with using PV panels to heat an electric boiler is that PV panels run at a small fraction of the efficiency of solar thermal panels. The other problem is storage. It's easier to have a large thermal water tank "battery" than huge banks of lead acid batteries to store the solar energy for use at night.

If you're planning to use solar for heat or DHW, hot water panels are the way to go, but certainly PV panels can be used to run the pumps.

You have to run the numbers for your electric rates and propane costs. Compare the two on a $ per million btu basis taking combustion efficiency into account.

Electricity: (cents per kWh)*2.93 = $ per million btu

Propane: ($ per gallon)*10.9/(AFUE decimal) = $ per million btu

If electricity ends up being close to or less than propane, I would still make provisions for a fuel burning boiler in the future. You never know which fuel might be cheaper in the future. Right now electricity seems to be lagging other fuels in price increases, but I believe it will eventually be the most expensive energy by far.